Compose schemas across documents and resolve types at the instance:
- xs:include, xs:import, and xs:redefine pull a transitive closure of schema
documents through an injected loader (resolved by schemaLocation), base
schemas first so the including schema wins; a redefine's nested definitions
override the schema it includes.
- substitution groups: an xs:element ref to a head also admits every element
that substitutes for it, expanded at parse time into a choice over the head
and its transitive members.
- xsi:type overrides an element's declared type with the named type at the
instance; XML Schema instance attributes are exempt from attribute checks.
The schema parser splits across XSDContext (shared tree helpers, document
collection, parsing context), XSDSimpleParser (simple types and facets), and
XSDParser (elements, complex types, model groups) to keep each within bounds.
Closes#66
Add Schema.Document compiling an xs:schema into global element declarations
and a named-type table, and validate(_:) checking instance documents end to
end. The parser supports global and local element declarations, named and
inline simple and complex types, sequence/choice/all groups with occurrence,
attribute uses, simple content (restriction/extension), the full facet set,
and recursive types via named references resolved during validation. Extends
ComplexType with a typeReference case and ComplexValidator with a type table
so recursive schemas are representable.
Closes#10
Add ComplexValidator validating an element against a ComplexType: attribute
uses (required, typed, unknown-attribute rejection) and the content model
(empty, simpleContent, elementOnly, mixed). Particles compile to a Thompson
NFA over element names honoring minOccurs/maxOccurs with sequence and choice
compositors; all groups are validated order-independently by counting. Child
elements are validated recursively against their declared types.
Closes#9
